On 2/12/2021 11:57 AM, Al Cooper wrote: > Add a UART driver for the new Broadcom 8250 based STB UART. The new > UART is backward compatible with the standard 8250, but has some > additional features. The new features include a high accuracy baud > rate clock system and DMA support. > > The driver will use the new optional BAUD MUX clock to select the best > one of the four master clocks (81MHz, 108MHz, 64MHz and 48MHz) to feed > the baud rate selection logic for any requested baud rate. This allows > for more accurate BAUD rates when high speed baud rates are selected. > > The driver will use the new UART DMA hardware if the UART DMA registers > are specified in Device Tree "reg" property. > > The driver also sets the UPSTAT_AUTOCTS flag when hardware flow control > is enabled. This flag is needed for UARTs that don't assert a CTS > changed interrupt when CTS changes and AFE (Hardware Flow Control) is > enabled. > > The driver also contains a workaround for a bug in the Synopsis 8250 > core. The problem is that at high baud rates, the RX partial FIFO > timeout interrupt can occur but there is no RX data (DR not set in > the LSR register). In this case the driver will not read the Receive > Buffer Register, which clears the interrupt, and the system will get > continuous UART interrupts until the next RX character arrives. The > fix originally suggested by Synopsis was to read the Receive Buffer > Register and discard the character when the DR bit in the LSR was > not set, to clear the interrupt. The problem was that occasionally > a character would arrive just after the DR bit check and a valid > character would be discarded. The fix that was added will clear > receive interrupts to stop the interrupt, deassert RTS to insure > that no new data can arrive, wait for 1.5 character times for the > sender to react to RTS and then check for data and either do a dummy > read or a valid read. Sysfs error counters were also added and were > used to help create test software that would cause the error condition. > The counters can be found at: > /sys/devices/platform/rdb/*serial/rx_bad_timeout_late_char > /sys/devices/platform/rdb/*serial/rx_bad_timeout_no_char > > Signed-off-by: Al Cooper <alcooperx@xxxxxxxxx> > --- > MAINTAINERS | 8 + > drivers/tty/serial/8250/8250_bcm7271.c | 1099 ++++++++++++++++++++++++ > drivers/tty/serial/8250/Kconfig | 11 + > drivers/tty/serial/8250/Makefile | 1 + > drivers/tty/serial/8250/bcm7271_uart.h | 158 ++++ > 5 files changed, 1277 insertions(+) > create mode 100644 drivers/tty/serial/8250/8250_bcm7271.c > create mode 100644 drivers/tty/serial/8250/bcm7271_uart.h > > diff --git a/MAINTAINERS b/MAINTAINERS > index 64c7169db617..bb6ad2fc4376 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -3582,6 +3582,14 @@ S: Supported > F: Documentation/devicetree/bindings/i2c/brcm,brcmstb-i2c.yaml > F: drivers/i2c/busses/i2c-brcmstb.c > > +BROADCOM BRCMSTB UART DRIVER > +M: Al Cooper <alcooperx@xxxxxxxxx> > +L: linux-usb@xxxxxxxxxxxxxxx This should probably be linux-serial, copy pasted from the USB entry down below presumably. -- Florian
